Magnetic chuck.



Eg Z

o. s. WALKER. MAGNETIC CHUCK. APPLICATION FILED FEB. I, I9I5.

Patented Apr. 25, 1916.

2 SHEETS-SHEET I.

` MKM/AM? 5%@ A' Mw 0. S. WALKER.

MAGNETIC CHUCK.

APPLICATION FILED FEB. I. I9l5.

1, 180,457. Patented Apr. 25, 1916.

2 SHEETS-SHEET 2.

UNITED STATES PATENT OFFICE.

OAKLEY l. WALKER, E WORCESTER, MASSACHUSETTS, AssIGNoR To o. s. WALKERCo., 0F WORCESTER, MASSACHUSETTS, A CORPORATION 0E MASSACHUSETTS.

MAGNETIC CHUCK.

Specification of Letters Patent.

Patented Apr. 25, 1916.

Application filed February 1, 1915. Serial No. 5,411.

To all whom t may concern:

Be it known that I, OAKLEY S.VWALKER, a citizen of the United States,residing at Worcester, in the County of Vorcester and Commonwealth ofMassachusetts, have invented a new and useful Improvement in MagneticChucks, of which the following, together with the accompanyinf"lirawings, is a specification. f

The present invention relates to magnetic chucks, and has particularreference to an improved construction for a device of this class wherebythe same aifords a work holding face which is peculiarly adapted for theretention of a large number of small pieces of iron or Steel placedthereon to be operated upon.

The said invention consists in the construction and arrangement ofparts, set forth in the following description and illustrated in theaccompanying drawings, in which- Figure 1 is a top plan view of a chuckembodying my invention. Fig. 2 is a vertical sectional view of saidchuck, taken substantially in a diametrical plane. Fig. 3 is a plan viewof the chuck shown in Fig. 1, the face plate thereof being removed todisclose the interior construction. Fig. 4 is a fragmentary verticalsectional view of a modified form of chuck.

Similar reference characters refer to similar parts in the differentfigures.

Referring to the drawings, the numeral 1 .denotes a circular base ofmagnetic metal,

providing a central aperture 2 for the attachment of a shaft or spindle,not shown,

` by which the chuck may be rotated. The

base l ai'ords an upwardly projecting central hub 3, and a concentricseries of spaced annular flanges 4, 5, 6, 7 and 8, with their topsurfaces flush with the top surface of said hub. The annular space 9thus formed between hub 3 and iiange 4, and the concentric annularspaces 10, 11, 12 and 13 similarly formed between the flanges 4 and 5, 5and 6, 6 and 7, and 7 and 8, respectively, receive the several circularmagnetizing coils 14, 15, 16, 17 and 18 of the chuck, as shown in Figs.2 and 3. These coils, in the present instance, are similarly wound andare connected in an electrical circuit in the manner hereinafterdescribed.

One terminal of the innermost coil 14, in the present instance the innerterminal, has connected thereto a conductor 19 passing through a Slot20v in the surrounding flange 4 and across the top of coil 15, as shownin Figs. 2 and 3. A Series of equidistant holes, leadmg upwardly throughthe flange 5 from an annular recess 21 on the under side of base l, areprovided for the reception of bushings 22 of fiber or other insulatingmaterial which afford shouldered heads 23 seating against the inner wallof recess 21. The

flange 5 is counterbored from the top, asl

shown at 24, Figs. 2 and 3, providing shoulders disposed somewhat abovethe upper ends of the bushings 22, upon which shoul- .aers are seatedwashers 25 of fiber or other insulating material. Screws 26, with theirheads within said counterbores and bearing against said washers, areextended through said bushings, their ends enteringan annular Contactring 27, to draw the same into the recess 21 against the heads 23 of thebushings 22 as the screws are tightened. The spaces left between thewashers 25 and the upper ends of the corresponding bushings 22 permitthe several parts to be drawn into snug engagement, as will be clearlyunderstood. The recess 21 is preferably filled with any suitablenon-conducting substance, such as sulfur, poured therein in a moltenState after the parts are assembled as above described, to hold themlirmly in position and to pre- Vent the access of dust, dirt and waterthereto. The construction above described is also applied to theattachment of a second Contact ring 28, by screws 29 passing through theflange 6; since said attachment is effected in precisely the same manneras the attachment of ring 27, it is unnecessary to describe the same indetail.

The conductor 19 leading from the inner terminal of coil 14 is connectedto one of the screws 26, as by insertion between a brass Washer and thehead of said screw, as

` shown in Figs. 2 and 3, thereby being placed in electrical connectionwith the ring 27, which is adapted to rotate in contact with astationary brush, not shown, included in the electrical circuit used toenergize the chuck. The outer terminal of coil 14 is connected, by aconductor 30 passing through a slot 31 in the flange 4, Fig. 3, with theouter terminal of the next adjacent coil 15, and the inner terminal ofcoil 15 is connected, by a conductor 32, Fig. 3, passing through one offlange `5, with the The outer termithe counterbores 24 in inner terminalof coil 16.

nal of coil 16 is connected, bya conductor 33 passing through one of thecounterbores 24 in flange G, with the outer terminal of coil 17, and theinner terminal of coil 17 is connected, by a conductor 34 passingthrough a slot 35 in the flange 7, with the inner terminal of coil 18.The outer terminal of coil 18 is connected, by a conductor 36 passingthrough a slot 37 in flange 7, with one of the screws 29 which securesthe second ring 28 in place, thereby completing the electrical circuitthrough the coils of the chuck when both of said rings 27 and 28 arerotating in contact with their respective brushes, not shown.

As previously stated, the several coils are similarly wound, and it willbe apparent from the above, are connected together in series. However,by reason of the above described connection of like terminals ofadjacent coils, the magnetizing effect of the current passingtherethrough is relatively opposite forvany two adjacent coils. Thiswill be made apparent in the effect4 roduced upon the hub 3 and theseveral anges 4, 5, 6, 7 and 8, which constitute, in effect, cores forthe several coils. Assuming that the passage of current through coil 14renders the hub 3 of positive magnetic polarity,- and the flange 4 ofnegative polarity, as indicated by the -land signs on Fig. 2, it will beclear that the magnetizing effect of the current in coil 15, which isrelatively opposite to that in coil 14, imparts negative polarity to theflange 4 and positive polarity to the next adjacent flange 5. The abovealternation of polarity for the several remaining flanges is carried outby the above described connection of the coils, and said flanges, forconvenience, have been design ated on Fig. 2 with alternating and signs.The work holding face ofthe chuck, which derives its magnetism throughcontact with the hub 3 and several flanges 4, 5, 6, 7 and 8 of the base1, is constituted in part by a centrally disposed structure presentingan arrangement of radiating non-magnetic gaps between sections ofopposite polarity, and in part by a concentric annular structurepresenting a plurality of circular nonmagnetic gaps between its severalsections. I have shown the central portion of said face as composed of amember 38, having a central aperture 39 coaxial with the hole 2 throughthe base and superposed at its central portion upon the hub 3, so as topartake of the magnetic polarity of said hub. Said member 38 provides aplurality of radiating spurs or teeth 40 which project outwardly overthe top of the flange 4, being cut away on their under sides, as shownat 41, tofavoid contact with said flange. The flange 4 supports anannular skeleton plate 42, surrounding member 38 and having a pluralityof inwardly projecting radial spurs 43 which enter the spaces betweenthe teeth 40 of member 38 and are cut away, on their under sides, asshown at 44, to avoid contact with the hub 3. As will be clearlyunderstood, the edges of the interlockinv teeth and spurs upon themember 38 anil4 plate 42, respectively, do not make contact, but presenta continuous narrow gap extending between all opposing portions thereof.Said gap is filled with non-magnetic material, the same in the presentinstance being preferably a brazed continuous joint between the two'parts, as indicated by the heavy black zigzag line 45 on Fig. 1 whichseparates the two sections of opposite magnetic polarity.

For the purpose of securing additional bearing surface-between the late42 and the flange 4, whereby the flow ol) magnetic lines of force fromsaid flange to said plate is facilitated, the contacting surface of theplate is broadened, and recessed so as to project downwardly in contactwith the sides of said flange, as shown at 46 in Fig. 2. The same detailof construction is adopted with respect toeach of the spaced rings 4748, 49 and 50 which are superposed respectively upon the other flanges5, 6, 7 and 8 of the base and constitute part of the circular gapportion of the work holding face. The outer peripheral side of the plate42 is inclined downwardly, so as to converge toward the oppositelyinclined inner peripheral face or side of the ring 47. This feature ofconstruction is also adopted with respect to the opposing sides of eachpair of adjacent rings 47, 48, 49 and 50, whereby the annular spa-cesbetween said rings are wedge shaped in cross section, as shown in Fig.2. Within said spaces are disposed the intermediate rings 51, 52, 53 and54 of corresponding cross-sectional shape, the same presenting outsidesurfaces, on the top of the face plate substantially equal in width tothe outside surfaces of the rings 47, 48, 49 and 50. The

ease of assemblage afforded by this construction of wedge shaped rings,whichdo not require the same accuracy of fit as do rings having straightvertical sides, makes it possible to braze the intermediate rings 51,52, 53 and 54 in position, thereby providingl the thin annularnon-magnetic gaps 55-62 inclusive, and thereafter to machine the uppersurfaces of said rings to correspond to the upper surfaces of the rings47 48, 49 and 50. This construction also permits the broadening of thebases of the rings 47, 48, 49 and 50, as above described, to insureadequate passage of the magnetic lines of force across the joints madewith the several cores, without increasing the spaces between saidcores, and also without necessitating a difference in the widths ofrings on the surface of the face plate.l

As will be seen, a work holding face of the character above described,presents a concentric series of magnetized sections which alternate inmagnetic polarity; and between adjacent sections' of said .series areinterposed concentric sections'pf magnetic metal which are not incontact"'with the magnetizing cores of the chuck,` said latter sectionsbeing separated from the magnetized sections by continuous relativelythin non-magnetic gaps. When a piece of work to be operated upon isdisposed so as to bridge one of the gaps 55--62 inclusive, being therebyin contact with one of the polarized and one of the unpolarized sectionsof the face plate, the magnetic circuit is completed by the leakage ofmagnetic lines of force across the thin gap between the unpolarizedsection and the next adjacent polarized section, causing said previouslyunpolarized section to partake of a polarity opposite to that of thepolarized section which is in contact with the work. The work is therebyheld by the How of magnetic lines `of force therethrough, as in anordinary magnetic chuck.

In addition to insuring a greater number of gaps to be bridged by thework, over work holding faces which do not provide such intermediatenormally unpolarized pole pieces, this construction permits amplespacesfor the coils of the chuck without unduly enlarging the polepieces which are in magnetic contact with the cores of said coils. Andwhile the holding power for 'a single given point upon the face of saidchuck is slightly decreased by reason of the necessity for the leakageof the magnetic lines across a non-magnetic gap to complete the magneticcircuit, yet the eiiiciency ofthe chuck for certain classes of Work isgreatly increased by reason of the great increase in the number ofholding points afforded. For it will be clear, that, for all varietiesof small work, such as washers and small rings, this construction ispeculiarly adapted, by reason of the relatively close arrangement of theholding points, it being practically impossible to dispose an article ofthis class upon the concentric portion of the tace plate withoutbridging two or more of the gaps 55-62 inclusive. And for work which isrelatively thin, and which therefore becomes magnetically saturated bythe passage of a relatively small number of lines of force,

this construction secures the most eicient retaining means possible, bygreatly multiplying the number of points at which such necessarilyrelatively small holding forces are applied to the work. Fig. 4 showsthe further application of this principle, in a chuck which is similarin construction to the chuck shown in Figs. 1, 2 and 3 except that thenumber of interposed normally un- !5 magnetized pole sections of theface plate is many times multiplied. In this form of the mvention therings 63, 64 and 65 which are superposed upon the cores or ianges 5, 6and 7 of the base l terminate in narrow tongues 66, 67 and 68,respectively, which are substantially of the same width as the severalinterposed concentric rings 69, which latter are brazed or otherwisejoined together t0 providea series of thin non-magnetic gaps 70 betweenthem, as shown in Fig. 4. The cutting away of the rings 63, 64 and 65 toform the narrow tongues 66, 67 and 68 provides shoulders 71 for thesupport of the intermediate series of rings 69, the inner and outerrings 69 of each of said series being separated from said tongues andfrom said shoulders by non-magnetic, preferably brazed, circular gaps72.

The structure above described affords the same advantages as thestructure shown in Figs. 1, 2 and 3 in multiplied degree, providing avery large number of points, each exerting a somewhat limited holdingpower upon the work which is disposed upon the face plate.

For yconvenience of manufacture and ease of assemblage, the severalrings comprising the annular gap portion of the face plate of myinvention may be made in halves, as shown in Fig. 1, the brazed joints73 of each ring being disposed preferably at right angles to the jointsof adjacent rings, so as to increase the structural strength of the iface plate. As shown in Fig. 2, the face plate is held securely to thebase 1 by an annular joint 74, the same being preferably formed betweenthe underside of the ring 50 and thetlange 8 by expanding a ring of softmetal into `Vthe annular space between said parts. The aboveconstruction provides .a seal against the leakage of water into thespace occupied by the coils; the

' only other openings into said coil space are effectually sealed by theprovision of the bushings 22 and their coperating screws and washers 26,29 and 25, respectively.

I claim,

1. In a magnetic chuckfa work holding face comprising sections ofopposite polarity, and an unpolarized section between said sections ofopposite polarity and separated v from each by a non-magnetic gap.

2. In a magnetic chuck, a work holdin face, comprising a plurality ofpolarized sections, with a plurality of interposed unpolarized sectionsbet-Ween adjacent polarized sections, separated from each other and fromsaid polarized sections by non-magnetic gaps.

3. In a magnetic chuck, a work holding face, comprising a series ofsections of alternating polarity, and a series of unpolarized sectionsinterposed between adjacent sections of said first mentioned series andseparated therefrom by non-magnetic gaps.

4. In a magnetic chuck, the combination with a member providing aplurality of spaced cores of alternating,r polarity, of a face platesuper-posed therein, comprisingJ a series of sections partaking of' thepolarity of said cores, and a series of unpolarized sections interposedbetween adjacent sections of said first mentioned series, and separatedtherefrom byrnon-magnetic gaps.

5. In a magnetic chuck, the combination with a member providing aplurality of spaced cores of alternating polarity, of a face platecomprising a series of sections superposed upon said cores, and a seriesof unpolarized sections interposed between the sections of the rstmentioned series and covering the spaces between said cores.

6. In a magnetic chuck, a member providing polarized cores, and a faceplate carried thereby consisting of pole pieces, each superposed on oneof said cores, and having its under surface recessed to it over theupper end of the core, whereby the contact area between pole piece andcore is increased.

7. In a magnetic chuck, a member providing a plurality of spaced cores,and a. face plate superposed upon said member comprising a plurality ofseparate sections, of which each alternate section makes contact withone of said cores.

8. In a. magnetic chuck, a member providing a plurality of spaced cores,and a face plate superposed upon said member, comprising a plurality ofSections greater in number than said cores, said sections havingnon-magnetic gaps between them, certain of said sections, correspondingin number to the number of cores, being each in contact with one of saidcores.

OAKLEY S. WALKER. lVitnesses:

NELLE WHALEN, PENELOPE COMBERBACH.

